The present invention relates to a device for recording in at least two planes radiation from a radiotherapy apparatus in a limited area at which the radiation is directed.
In particular, the invention relates to a device for determining the resulting radiation, which from a number of different directions hits a plane or a volume, by recording the radiation on media sensitive to radiation, such as films, semiconductors, ionization chambers, etc., in defined positions and simultaneously or later evaluating recorded radiation data with respect to the distribution of the radiation in time and space by means of a read-out device. The device is especially suited for accurate spatial determination relative to given references of geometrically defined radiation distributions.
The device is also suited for quality assurance of a whole precision radiation procedure by allowing target volumes to be simulated, which volumes can be determined as regards shape and position by medical, image-creating equipment, such as magnetic resonance imaging, computer tomography, etc., for planning treatment of precision radiation and for verifying radiation based on planning.
Furthermore, the device is above all intended to be used together with ELEKTA AB""s gamma knife which is presented in the leaflet xe2x80x9cLeksell Gamma Knife, Model C, System Description with Technical Overviewxe2x80x9d, cf. U.S. Pat. Nos. 4,780,898 and 5,528,651. Here Leksell Gamma Plan(copyright) is advantageously used.
U.S. Pat. No. 5,511,107 discloses what is referred to as a phantom assembly for measuring radiation dose distributions in order to verify the radiation dose applied in a target area. The phantom assembly is constructed of material that is the radiological equivalent of the part of a patient""s body that is to be treated, in the presented embodiment the patient""s skull. A radiation sensitive film is inserted into a slit in the phantom assembly, a treatment dose is applied to the phantom and the film is analyzed with respect to the radiation exposure. In one embodiment of the phantom, three films have been inserted into one another in three mutually orthogonal planes (in the X, Y and Z directions) and then eight partial cubes have been applied around the films, one in each quadrant, so that a large cube which encloses the films is formed. The partial cubes are kept together by an enclosing casing. The partial cubes are to a certain extent movable in relation to one another, thereby affecting the precision in the positioning of the films and thus the determination of the target area. In addition, the radiation dose cannot be measured in the center of the phantom (the area with the common intersection point of the films (origin)), the center usually being the most interesting area.
The international patent application PCT/CA99/01070 (WO 00/29871) discloses a phantom with films for stereo-tactic dosemetry. The phantom contains a cassettebox with a plurality of films which are positioned parallel to one another and are separated by distance means of a material which in terms of radiation is similar to the part of the patient""s body that is to be treated. The phantom is rotatable about an axis to which all films are parallel. Thus, the plane of the films cannot be made to assume different angles relative to the attachment of the phantom so that a defined center plane of the phantom moves around a fixed center point in the phantom between a position parallel to the attachment and a position perpendicular to the attachment, which is necessary to be able to accurately determine the radiation in a three-dimensional area.
The object of the invention is to provide a device by means of which the common point (iso center) at which the radiation is directed from different directions, is determined with high geometric precision in connection with radiation.
Another object of the invention is to provide a device by means of which the geometrical radiation dose distribution in a radiotherapy apparatus can be determined.
Yet another object of the invention is to provide a device by means of which the total radiation dose can be measured during a simulated treatment process.
According to the invention, these objects are achieved by means of a device as stated by way of introduction, which is characterized in that the device comprises a dimensionally stable frame which is adapted to be arranged in a defined position relative to said radiation sources, an attachment on the frame for a recording means, and a recording means which extends from the attachment at an acute angle to the frame along an axis of rotation and to the center of the frame and which is adapted to assume at least two defined rotational positions on said axis, that the recording means exhibits a surface for supporting a radiation recording unit, which surface is located in a plane that forms an acute angle with said axis of rotation, and that the plane of the surface when rotating the recording means is adapted to turn on a single pivot point which is fixed relative to the frame.
Further developments of the invention are evident from the features stated in the subclaims.